Heretofore, gear grinding machines have been provided to efficiently finish the faces of the teeth of a heat-treated gear by grinding the gear with a threaded grinding wheel, which is a grinding tool. The sharpness of the threaded grinding wheel decreases due to the wear thereof as grinding is repeated. Accordingly, after a predetermined number of gears have been ground, the worn threaded grinding wheel needs to be dressed to restore the sharpness of the faces of the threads thereof.
For this reason, conventional gear grinding machines have the dressing function of dressing a worn threaded grinding wheel with a dresser. Such a gear grinding machine having the dressing function is disclosed in, for example, Patent Document 1.
On the other hand, of gears, internal gears are frequently used in automotive transmissions and the like. Recently, there has been a demand for the improvement of machining accuracy for the purpose of reducing the vibration and noise of such transmissions. Accordingly, internal gear grinding methods for finish-grinding an internal gear with a barrel-shaped threaded grinding wheel with high accuracy have been heretofore disclosed, for example, in Non-Patent Document 1.